Acheron Class Destroyer (1910)

Twenty-nine destroyers of the Acheron Class (redesignated the "I" class in October, 1913)[1]) were completed between 1911 and 1912. Twenty were part of the 1910-1911 Programme, and an additional six (later nine) Specials were ordered.

They were the last Royal Navy destroyers to use the 12-pdr gun.

Most served in the First Destroyer Flotilla where their 60 test runs of 21-in Mark II torpedoes in the first half of 1916 were judged 87% likely to endanger the enemy.[2] Other units served elsewhere; Oak served as the dispatch vessel to Iron Duke and Firedrake and Lurcher served with submarine flotillas in Harwich.[3]

Radio

In 1912, eighteen of the new destroyers were fitted with Destroyer Sets. The pace of this initiative suggests that all units were probably so equipped by the start of the war.[4][Inference]

Searchlights

Badger, at least, had a (hydraulic?) control system to control her searchlights whose success prompted an Admiralty order to fit the same gear to the earlier Beagle class.[5] Just four days later, the twenty Acherons of the First Destroyer Flotilla were also ordered to have this equipment added.[6]

Performance

Turning performance was widely variable, as it had been with the preceding Acorn class.

Ferret achieved four miles to the ton of coal at 27.5 knots. Redpole topped out at a spry 30.61 knots in rough weather!

Sight lines were 16.5 inches above the bore, and 15 inches left for the layer and 17.46 inches above and 12.5 inches right for the trainer. There were open sights on both sides and temperature correctors were provided.

During the war, some of the ships had their aft 4-in gun landed to accommodate depth charges.[11]

In late 1913, guards ("complete with eyes and chains") were ordered to protect the open sights.[12]

12-pdr Guns

Two 12-pdr guns were mounted just after the break of the forecastle deck, port and starboard.[13]

They were 12-pdr 12 cwt Q.F. guns on P. VI mountings with 30 common and 70 lyddite rounds per gun (plus 10 practice rounds per gun per quarter),[14] the same weapon as since the "Tribal" group. The mountings could elevate to 20 degrees and depress to 10.

The sights were gear-worked with a range gearing constant of 30.857, and range dials for 2200 fps, 2175 fps, 1-in and .303-in aiming rifles. They could elevate to 11.5 degrees, or 6,075 yards full charge). There was no means of correcting for muzzle velocity. It was a simple design compared to that used in the Acorn class.

Drift was corrected by inclining guides to the sight carrier 2 degrees. Sighting lines for the layer were 11.558 inches above the bore and 10.106 inches left. The trainer's sighting lines were 12.270 inches above the bore and 10.881 inches right. Open sights and head rests were provided on both sides. There was no temperature corrector.

Gun trials showed that the sightsetter (probably for the 12-pdr guns)[Inference] was in danger of falling overboard when firing at some bearings.[15]

In late 1913, the P. Mark V and VI gun mountings had percussion firing gear ordered for them.[16]

Torpedoes

Two single 21-in tubes on the centre line.

Other Weapons

Depth charges were added during the war to many of the ships, requiring some to surrender their aft 4-in gun.[17]

Fire Control

By 1915, at least, these ships also had fixed voice pipes installed between decks with the last lengths being flexible (one voice pipe for gunnery, one for torpedoes) fitted between bridge and guns, torpedo tubes, and searchlights. A third voicepipe, entirely flexible, ran from bridge to the forward gun.[18]

Instruments

Rangefinders

A 1-m base rangefinder was supplied to all destroyers of the "Tribal" class through "L" class around 1916, but this was later withdrawn.[20]

Torpedo Control

Electrical Torpedo Control Instruments[21]found in most or all "Acheron" class destroyers

A single sighting position was located high up in the centre of the bridge, thus requiring only a single set of firing pushes or keys as well as keys for operating a buzzer at the forward torpedo mount and a rattler at the aft mount.[22]

The data instruments used were electrical. A single Mark I deflection transmitter at the control position, and separate order transmitters and keys, one for the forward tubes and one for the aft. Each torpedo mount had a combined receiver for these signals.[23]

Alterations

In July 1914, the four Thornycroft and Yarrow "specials" (Acheron, Ariel, Attack and Archer) were to have lockable gratings added to control access to their Spirits and Electrical Store Rooms. At the same time, requests to fit a new pattern stern light to these ships was deferred until trials with it were complete, and a price quote was requested before open trainers' sights would be added.[24]

By November 1918, Ferret and Sandfly were fitted to carry 38 mines, as they were operating with the Twentieth Destroyer Flotilla which was uniformly capable in this regard. The torpedo tubes and guns removed when the mines were shipped could be placed back aboard with enough notice.[25]